<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <button class="btn"></button>
    <h1>h1大标题</h1>
    <h2>h2</h2>
    <span>aaaaaaaa</span>
    <p><strong>a</strong>ssssss</p>
    <script>
        document.querySelector(".btn") .occlick(alert('aaaaa'))
    </script>
</body>
</html>
